Hi,

I have a situation in one of my customers. Case 240503-407 .

Here is the situation : 

the customer start with a 3 nodes HSX cluster with 24x16TB disk

He adds a fourth node, and because of a shortage of 16TB disk availability he goes with 20TB disk (also with 768GB of ram)

Now if we look at the disks on an 16TB node we see :

/dev/sdn                                   17T   13T  3.7T  78% /hedvig/d15

/dev/sdc                                   17T   14T  3.4T  80% /hedvig/d4

/dev/sde                                   17T   13T  3.7T  78% /hedvig/d6

/dev/sdw                                   17T   13T  3.7T  78% /hedvig/d24

/dev/sdd                                   17T   13T  3.8T  78% /hedvig/d5

and if we look at the disks on a 20TB node we see :

/dev/sdt                                   19T   14T  4.3T  77% /hedvig/d22
/dev/sdx                                   19T   14T  4.5T  76% /hedvig/d26
/dev/sde                                   19T   14T  4.4T  77% /hedvig/d7
/dev/sdf                                   19T   14T  4.3T  77% /hedvig/d8
/dev/sds                                   19T   15T  4.0T  79% /hedvig/d21

The support said :

- The disk here already seems to be utilizing the 20 TB that is assigned.
- When checked internally, for hyperscale X, the check on the code side would be " equal to or higher ". This means that 20TB could be utilized fully here, which is seen in the disks as well.
- The CAP of 16TB was for hyperscale 1.5, and since we are on hyperscale X here, you can continue to add nodes with 20TB here.

Does it mean they were formated with all the extra space but the Storage Pool won’t use it ?

Also what is happening if we add more nodes in this cluster with 20TB disks ?

The space will never be used ? 

If we end up with only 20TB disks in all the nodes, the cluster will only use 16TB of disk space ?

Is there a procedure somewhere on how to replace a node inside a cluster ?

Or we just pull the power of the node we want to replace and reimage a new node in this cluster ?

Answer from support ticket 240503-407 :

As much as I want it to be shared with you, there is no documentation available for the replacement of a node.
Only documentation would be to replace a disk here.
 
You could raise the concern with the accounts team which could help you in a similar scenario.
From the support perspective, I assure that there are no such documentation/ step that is available.

Those it means, when you start a cluster with a specifique disk size, the only way to change it is to start a brand new cluster ?